TRIGONAL-LANTERN DINUCLEAR COMPOUNDS OF DIIRON(I,II) - THE SYNTHESIS AND CHARACTERIZATION OF 2 HIGHLY PARAMAGNETIC FE-2(AMIDINATO)(3) SPECIES WITH SHORT METAL-METAL BONDS .1.

Two examples of a new type of trigonal-lantern compound in which a for mal Fe-2(3+) unit is bridged by three amidinato groups are formed by r eacting FeCl2(HDPhF)(2) (HDPhF=N,N'-diphenylformamidine) and FeCl2(HDP hBz)(2) (HDPhBz=N,N'-diphenylbenzamidine) with NaEt3BH and methyllithi um in THF. The isolated crystalline products, Fe-2(amidinato)(3), have been structurally characterized by X-ray crystallography at -60 degre es C. Crystal data for Fe-2(DPhF)(3) (I): monoclinic, space group C2/c , a=17.154(4), b=8.255(1), c=23.400(5) Angstrom, beta=93.38(1)degrees, Z=4; and for Fe-2(DPhBz)(3) . 2C(6)H(6) (II): trigonal, space group < R(3)over bar>c, a=11.237(2), c=76.510(7) Angstrom, Z=6. The Fe-Fe bond distances, 2.2318(8) and 2.198(2) Angstrom for compounds I and II, re spectively, are the shortest known for any diiron compound. The room t emperature magnetic susceptibilities of 7.81 and 7.53 B.M. for I and I I and the EPR spectrum of I in a toluene glass (10 K) which shows two signals at g values of 1.99 and 7.94 are consistent with the presence of seven unpaired electrons in an axially symmetric environment.